A/N.: Inspired by the user name Mistress Slytherin (userID: 9214710)
Many revered the name Salazar Slytherin, but few even knew even at the time of the founders, that Slytherin was a woman. She was named the heir of her family, and as such, had to hide her gender, afraid of forced marriages and ridicule. Her only friends knew, of course, but it led to heartache and fury later, for Salazar fell in love with her only male friend, Godric Gryffindor, whose face she painstakingly formed to the wall of her hidden chamber, initially designed as a shelter, for the time the castle was taken over. Admittedly it wasn't a likely scenario, but she liked to plan for every possibility.
Godric took years before he even recognized the love in his skilled, wiry and androgynous friend, with some help, and took no time to sweep her from her feet. This led to a fiery and almost violent relationship, but while Salazar's love was true, Godric only possessed lust that burned out quickly. He left her broken.
Salazar was strong though, determined, and she found meaning in her new plans. She travelled wide and far, at last bringing a small egg with her, and a new view of the world when she came back. She cared for the egg, watched it hatch and taught her basilisk familiar all she could. She left the instructions of the openings in the headmaster's chamber, hoping for worthy leaders at least every 200 years, so they could feed, talk to and care for her pet.
Sadly the knowledge was lost as soon as the first headmaster took his seat, leaving only myths and a slowly maddening snake, once left to save and guard the school and fortress.
She saw in her travels how muggles acted when finding out about magic, more than once, she showed her talents in different places just to be forced to flee every time. She concluded that no matter how the knowledge was presented, those without the ability were going to fear, envy and hate magic and anything and anyone magical.
Though she tried to tell this to the others, they took it as an attack, not even trying to hear her out. It was mostly Godric's doing as he took everything she said as revenge for 'her bruised ego' and said she was just behaving like any woman scorned. The other two were not so rush, but couldn't stand up to the headstrong Gryffindor.
Salazar left, and Godric made sure the gossip turned on her, leaving the false preconception of her house for years to come.
Though she felt betrayed, she didn't leave the world without heirs. She married out of necessity and convenience, but had a stable and trusting relationship, starting the purebloods' way of arranged marriages and made countless discoveries in potions and various other arts.
Her teachings faded, her family degenerated, her familiar dead now. She was a magnificent person, her one mistake was falling for someone who was rash and couldn't appreciate her.